1. Field of the Invention
This invention relates to a push-button switch of the automatic returning type which employs a click rubber element.
2. Description of the Related Art
Various push-button switches of the type mentioned are already known, and an exemplary one of such conventional push-button switches is shown in FIG. 6.
Referring to FIG. 6, the conventional push-button switch shown includes an insulating case 1 in the form of a box which is open at the top thereof. A recess 3 is formed on an inner bottom face 2 of the insulating case 1, and a pair of fixed contacts 4 are disposed in the recess 3. A click rubber element 5 is placed, at a base portion 5a extending outwardly downwards therefrom, on the inner bottom face 2 of the insulating case 1. The click rubber element 5 is held in the insulating case 1 with the base portion 5a thereof surrounded by a holding wall 6 of the insulating case 1. A stem 8 is placed on the top of the click rubber element 5 and has a flange 9 formed at the bottom thereof. The flange 9 of the stem 8 is fitted in an annular recess 10 formed at an upper portion of an inner face of the holding wall 6 of the insulating case 1. The stem 8 is normally urged upwardly by the click rubber element 5 to a normal position in which the flange 9 thereof is engaged with an upper end of the recess 10. When the stem 8 is depressed downwardly from the normal position, it moves downwardly while the flange 9 thereof slides on an annular bottom face of the recess 10, whereupon a lower face the stem 8 pushes the top of the click rubber element 5 downwardly to resiliently deform the click rubber element 5 until the movable contact 7 thereon are contacted with the fixed contacts 4 to short-circuit them to put the push-button switch into an on-state. Then, when the stem 8 is released, the resiliently deformed click rubber element 5 restores its original condition by its own resilient returning force, whereupon it pushes up the stem 8. Consequently, the movable contact 7 is spaced away from the fixed contacts 4 so that the push-button switch is returned into an original off-state.
However, according to the structure of the conventional push-up switch described above, since the flange 9 of the stem 8 slides on the bottom face of the annular recess 10 of the inner face of the holding wall of the insulating case 1, the stem 2 will not rattle during depression or returning upward movement of the stem 8. However, since the annular recess 10 which provides a sliding face for the flange 9 of the stem 8 is formed at the upper portion of the holding wall 6 for the click rubber element 5, the insulating case 1 has a great thickness or dimension in the vertical direction as much, and accordingly, there is a problem that the entire push-button switch has a corresponding great thickness in the vertical direction. Further, if the thickness of the insulating case 1 is reduced, then there may be another problem that it is difficult to assure a sufficient sliding face for the stem 8 and the stem 8 may rattle upon depression or returning thereof.